The present invention is directed to printing processes. More specifically, the present invention is directed to printing processes, such as ink jet printing, wherein a fluid is applied to the print substrate either prior to or subsequent to application of the ink image with the printer. One embodiment of the present invention is directed to a fluid deposition apparatus comprising (a) a fluid supply, (b) a porous fluid distribution member in operative connection with the fluid supply, enabling wetting of the fluid distribution member with a fluid, and (c) a porous metering membrane situated on the fluid distribution member, whereby the metering membrane enables uniform metering of the fluid from the fluid distribution member onto a substrate.
Ink jet printing systems generally are of two types: continuous stream and drop-on-demand. In continuous stream ink jet systems, ink is emitted in a continuous stream under pressure through at least one orifice or nozzle. The stream is perturbed, causing it to break up into droplets at a fixed distance from the orifice. At the break-up point, the droplets are charged in accordance with digital data signals and passed through an electrostatic field which adjusts the trajectory of each droplet in order to direct it to a gutter for recirculation or a specific location on a recording medium. In drop-on-demand systems, a droplet is expelled from an orifice directly to a position on a recording medium in accordance with digital data signals. A droplet is not formed or expelled unless it is to be placed on the recording medium.
Since drop-on-demand systems require no ink recovery, charging, or deflection, the system is much simpler than the continuous stream type. There are three types of drop-on-demand ink jet systems. One type of drop-on-demand system has as its major components an ink filled channel or passageway having a nozzle on one end and a piezoelectric transducer near the other end to produce pressure pulses. The relatively large size of the transducer prevents close spacing of the nozzles, and physical limitations of the transducer result in low ink drop velocity. Low drop velocity seriously diminishes tolerances for drop velocity variation and directionality, thus impacting the system's ability to produce high quality copies. Drop-on-demand systems which use piezoelectric devices to expel the droplets also suffer the disadvantage of a slow printing speed.
Another type of drop-on-demand system is known as acoustic ink printing. As is known, an acoustic beam exerts a radiation pressure against objects upon which it impinges. Thus, when an acoustic beam impinges on a free surface (i.e., liquid/air interface) of a pool of liquid from beneath, the radiation pressure which it exerts against the surface of the pool may reach a sufficiently high level to release individual droplets of liquid from the pool, despite the restraining force of surface tension. Focusing the beam on or near the surface of the pool intensifies the radiation pressure it exerts for a given amount of input power. These principles have been applied to prior ink jet and acoustic printing proposals. For example, K. A. Krause, "Focusing Ink Jet Head," IBM Technical Disclosure Bulletin, Vol 16, No. 4, September 1973, pp. 1168-1170, the disclosure of which is totally incorporated herein by reference, describes an ink jet in which an acoustic beam emanating from a concave surface and confined by a conical aperture was used to propel ink droplets out through a small ejection orifice. Acoustic ink printers typically comprise one or more acoustic radiators for illuminating the free surface of a pool of liquid ink with respective acoustic beams. Each of these beams usually is brought to focus at or near the surface of the reservoir (i.e., the liquid/air interface). Furthermore, printing conventionally is performed by independently modulating the excitation of the acoustic radiators in accordance with the input data samples for the image that is to be printed. This modulation enables the radiation pressure which each of the beams exerts against the free ink surface to make brief, controlled excursions to a sufficiently high pressure level for overcoming the restraining force of surface tension. That, in turn, causes individual droplets of ink to be ejected from the free ink surface on demand at an adequate velocity to cause them to deposit in an image configuration on a nearby recording medium. The acoustic beam may be intensity modulated or focused/defocused to control the ejection timing, or an external source may be used to extract droplets from the acoustically excited liquid on the surface of the pool on demand. Regardless of the timing mechanism employed, the size of the ejected droplets is determined by the waist diameter of the focused acoustic beam. Acoustic ink printing is attractive because it does not require the nozzles or the small ejection orifices which have caused many of the reliability and pixel placement accuracy problems that conventional drop on demand and continuous stream ink jet printers have suffered. The size of the ejection orifice is a critical design parameter of an ink jet because it determines the size of the droplets of ink that the jet ejects. As a result, the size of the ejection orifice cannot be increased, without sacrificing resolution. Acoustic printing has increased intrinsic reliability because there are no nozzles to clog. As will be appreciated, the elimination of the clogged nozzle failure mode is especially relevant to the reliability of large arrays of ink ejectors, such as page width arrays comprising several thousand separate ejectors. Furthermore, small ejection orifices are avoided, so acoustic printing can be performed with a greater variety of inks than conventional ink jet printing, including inks having higher viscosities and inks containing pigments and other particulate components. It has been found that acoustic ink printers embodying printheads comprising acoustically illuminated spherical focusing lenses can print precisely positioned pixels (i.e., picture elements) at resolutions which are sufficient for high quality printing of relatively complex images. It has also has been discovered that the size of the individual pixels printed by such a printer can be varied over a significant range during operation, thereby accommodating, for example, the printing of variably shaded images. Furthermore, the known droplet ejector technology can be adapted to a variety of printhead configurations, including (1) single ejector embodiments for raster scan printing, (2) matrix configured ejector arrays for matrix printing, and (3) several different types of pagewidth ejector arrays, ranging from single row, sparse arrays for hybrid forms of parallel/serial printing to multiple row staggered arrays with individual ejectors for each of the pixel positions or addresses within a pagewidth image field (i.e., single ejector/pixel/line) for ordinary line printing. Inks suitable for acoustic ink jet printing typically are liquid at ambient temperatures (i.e., about 25.degree. C.), but in other embodiments the ink is in a solid state at ambient temperatures and provision is made for liquefying the ink by heating or any other suitable method prior to introduction of the ink into the printhead. Images of two or more colors can be generated by several methods, including by processes wherein a single printhead launches acoustic waves into pools of different colored inks. Further information regarding acoustic ink jet printing apparatus and processes is disclosed in, for example, U.S. Pat. No. 4,308,547, U.S. Pat. No. 4,697,195, U.S. Pat. No. 5,028,937, U.S. Pat. No. 5,041,849, U.S. Pat. No. 4,751,529, U.S. Patent 4,751,530, U.S. Pat. No. 4,751,534, U.S. Pat. No. 4,801,953, and U.S. Pat. No. 4,797,693, the disclosures of each of which are totally incorporated herein by reference. The use of focused acoustic beams to eject droplets of controlled diameter and velocity from a free-liquid surface is also described in J. Appl. Phys., vol. 65, no. 9 (1 May 1989) and references therein, the disclosure of which is totally incorporated herein by reference.
Still another type of drop-on-demand system is known as thermal ink jet, or bubble jet, and produces high velocity droplets and allows very close spacing of nozzles. The major components of this type of drop-on-demand system are an ink filled channel having a nozzle on one end and a heat generating resistor near the nozzle. Printing signals representing digital information originate an electric current pulse in a resistive layer within each ink passageway near the orifice or nozzle, causing the ink in the immediate vicinity to evaporate almost instantaneously and create a bubble. The ink at the orifice is forced out as a propelled droplet as the bubble expands. When the hydrodynamic motion of the ink stops, the process is ready to start all over again. With the introduction of a droplet ejection system based upon thermally generated bubbles, commonly referred to as the "bubble jet" system, the drop-on-demand ink jet printers provide simpler, lower cost devices than their continuous stream counterparts, and yet have substantially the same high speed printing capability.
The operating sequence of the bubble jet system begins with a current pulse through the resistive layer in the ink filled channel, the resistive layer being in close proximity to the orifice or nozzle for that channel. Heat is transferred from the resistor to the ink. The ink becomes superheated far above its normal boiling point, and for water based ink, finally reaches the critical temperature for bubble formation or nucleation of around 280.degree. C. Once nucleated, the bubble or water vapor thermally isolates the ink from the heater and no further heat can be applied to the ink. This bubble expands until all the heat stored in the ink in excess of the normal boiling point diffuses away or is used to convert liquid to vapor, which removes heat due to heat of vaporization. The expansion of the bubble forces a droplet of ink out of the nozzle, and once the excess heat is removed, the bubble collapses on the resistor. At this point, the resistor is no longer being heated because the current pulse has passed and, concurrently with the bubble collapse, the droplet is propelled at a high rate of speed in a direction towards a recording medium. The resistive layer encounters a severe cavitational force by the collapse of the bubble, which tends to erode it. Subsequently, the ink channel refills by capillary action. This entire bubble formation and collapse sequence occurs in about 10 microseconds. The channel can be refired after 100 to 500 microseconds minimum dwell time to enable the channel to be refilled and to enable the dynamic refilling factors to become somewhat dampened. Thermal ink jet processes are well known and are described in, for example, U.S. Pat. No. 4,601,777, U.S. Pat. No. 4,251,824, U.S. Pat. No. 4,410,899, U.S. Pat. No. 4,412,224, and U.S. Pat. No. 4,532,530, the disclosures of each of which are totally incorporated herein by reference.
U.S. Pat. No. 5,380,769 (Titterington et al.), the disclosure of which is totally incorporated by reference, discloses reactive ink compositions that utilize at least two reactive components, a base ink component and a curing component, that are applied to a receiving substrate separately. The base ink component includes an ink carrier, a compatible colorant, and a crosslinkable constituent, and the curing component is a crosslinking agent. Upon exposure of the base ink component to the curing component, at least a portion of the ink is crosslinked to provide a printed image that is durable and abrasion resistant.
U.S. Pat. No. 5,428,384 (Richtsmeier et al.), the disclosure of which is totally incorporated herein by reference, discloses a color ink jet printer having a heating blower system for evaporating ink carriers from the print medium after ink jet printing. A preheat drive roller engages the medium and draws it to a print zone. The drive roller is heated and preheats the medium before it reaches the print zone. At the print zone, a print heater heats the underside of the medium via radiant and convective heat transfer through an opening pattern formed in a print zone heater screen. The amount of heat energy is variable, depending on the type of the print medium. A crossflow fan at the exit side of the print zone direct an airflow at the print zone in order to cause turbulence at the medium surface being printed and further accelerate evaporation of the ink carriers from the medium. An exhaust fan and duct system exhausts air and ink carrier vapor away from the print zone and out of the printer housing.
U.S. Pat. No. 5,457,523 (Facci et al.), the disclosure of which is totally incorporated herein by reference, discloses a device for applying an electrical charge to a charge retentive surface by transporting ions in a fluid media and transferring the ions to the member to be charged across the fluid media/charge retentive surface interface. The fluid media is positioned in contact with a charge retentive surface for depositing ions onto the charge retentive surface. In one specific embodiment, the fluid media is a ferrofluid material wherein a magnet is utilized to control the position of the fluid media, which, in turn, can be utilized selectively to control the activation of the charging process.
U.S. Pat. No. 5,602,626 (Facci et al.), the disclosure of which is totally incorporated herein by reference, discloses an apparatus for applying an electrical charge to a charge retentive surface by transporting ions through an ionically conductive liquid and transferring the ions to the member to be charged across the liquid/charge retentive surface interface. The ionically conductive liquid is contacted with the charge retentive surface for depositing ions onto the charge retentive surface via a wetted donor blade supported within a conductive housing, wherein the housing is coupled to an electrical power supply for applying an electrical potential to the ionically conductive liquid. In one specific embodiment, the charging apparatus includes a support blade for urging the donor blade into contact with the charge retentive surface and a wiping blade for wiping any liquid from the surface of the charge retentive surface as may have been transferred to the surface at the donor blade/charge retentive surface interface.
U.S. Pat. No. 5,561,505 (Lewis), the disclosure of which is totally incorporated herein by reference, discloses an apparatus for applying an electrical charge to a charge retentive surface by transporting ions through an ionically conductive liquid and transferring the ions to the member to be charged across the liquid/charge retentive surface interface. The tonically conductive liquid is contacted with the charge retentive surface for depositing ions onto the charge retentive surface via a wetted donor blade supported within a mechanically sealable housing adapted to permit movement of the wetted donor blade from an operative position in contact with the charge retentive surface, to a nonoperative position stored within the housing to prevent loss of the tonically conductive liquid in its liquid or vapor form so as to extend the functional life of the apparatus. In one specific embodiment, a wiper blade may be provided for removing any liquid droplets from the surface of the photoreceptor as may have been transferred at the donor blade/charge retentive surface interface.
Copending application U.S. Ser. No. 08/523,322, entitled "Segmented Flexible Heater for Drying a Printed Image," filed Aug. 30, 1995, with the named inventors Thomas F. Szlucha and John H. Looney, the disclosure of which is totally incorporated herein by reference, discloses a segmented flexible heater disposed adjacently to a paper path in a printing machine for heating a recording medium before printing and during printing. The segmented flexible heater includes a curved first portion for preheating the paper and a substantially planar second portion for heating the paper in a print zone wherein the second portion generates heat energy having a temperature greater than the heat energy generated by the first portion. The first portion includes apertures for accommodating drive rollers for moving the recording medium into the print zone area heated by the second portion. The apertures in the flexible heater provide for continuous heating of the recording medium before and during heating. The second portion is preferably at least two printing swaths wide to prevent thermal shock to the portion of the printing medium being printed on.
Copending application U.S. Serial No. 09/069,698, filed concurrently herewith, with the named inventors Joel A. Kubby, Lisa A. DeLouise, and David A. Mantell, the disclosure of which is totally incorporated herein by reference, discloses the processing of plain paper through a plain paper optimizer system prior to image formation on a recording surface. The optimizer system adds a fixing fluid during application of pressure and, optionally, heat to the paper surface. The surface contacted by the fixing fluid is enhanced, forming images of improved print quality. In one embodiment, plain paper is treated in an optimizer system, which comprises a heat and fuser assembly with silicone oil as the fixing fluid, and is transported into the print zone of an ink jet printer. Images printed on the treated surface demonstrate improvements in image quality manifested by reduction of both edge raggedness and intercolor bleeding.
Copending application U.S. Serial No. 09/069,111, filed concurrently herewith, with the named inventors Thomas W. Smith, Samuel Kaplan, Kathleen M. McGrane, and David J. Luca, the disclosure of which is totally incorporated herein by reference, discloses a process which comprises (a) applying to a substrate a fixing fluid which comprises a material selected from the group consisting of (1) block or graft copolymers of dialkylsiloxanes and polar, hydrophilic monomers capable of interacting with an ink colorant to cause the colorant to become complexed, laked, or mordanted, (2) organopolysiloxane copolymers having functional side groups capable of interacting with an ink colorant to cause the colorant to become complexed, laked, or mordanted, (3) perfluorinated polyalkoxy polymers, (4) perfluoroalkyl surfactants having thereon at least one group capable of interacting with an ink colorant to cause the colorant to become complexed, laked, or mordanted, and (5) mixtures thereof; (b) incorporating into an ink jet printing apparatus an ink composition which comprises water and a colorant which becomes complexed, laked, or mordanted upon contacting the fixing fluid; and (c) causing droplets of the ink composition to be ejected in an imagewise pattern onto the substrate.
While known compositions and processes are suitable for their intended purposes, a need remains for improved ink jet printing methods. In addition, a need remains for improved thermal ink jet printing processes. Further, a need remains for ink jet printing processes wherein the resulting images exhibit improved image permanence. Additionally, a need remains for ink jet printing processes wherein the resulting images exhibit improved waterfastness. There is also a need for ink jet printing processes wherein the resulting images have improved archival quality. In addition, there is a need for ink jet printing processes wherein the resulting images are bright and intense. Further, there is a need for ink jet printing processes wherein the image quality of the resulting prints is independent of the specific paper employed in the printing process. Additionally, there is a need for ink jet printing processes wherein the resulting images exhibit reduced wet smear. A need also remains for ink jet printing processes wherein the above noted advantages can be achieved at a reasonably low cost. In addition, a need remains for ink jet printing processes wherein the resulting images have sharp edges or boundaries and wherein ink feathering and intercolor bleed between adjacent colors is minimized. There is also a need for cost effective apparatus and processes for applying a fixing fluid to a substrate in an ink jet printer.